The present invention relates to the manufacture of tires. More precisely, it relates to the depositing of cords to constitute a tire reinforcement. More particularly, it proposes means suitable for manufacturing such a reinforcement on a form similar or identical to the form of the internal cavity of the tire, that is to say a substantially toroidal form, supporting the tire blank during manufacture thereof.
In this technical field, processes and apparatus are already known which permit incorporation of the manufacture of the tire reinforcements into assembly of the tire itself. This means that, rather than having recourse to semi-finished products, such as reinforcement plies, one or more reinforcements are produced in situ, at the time of manufacture of the tire, from a cord spool. Of these processes and apparatus, the solution described in U.S. Pat. No. 5,453,140 is most particularly adapted to the production of carcass reinforcements on a rigid core, the outer surface of which corresponds substantially to the form of the internal cavity of the finished tire. This patent discloses equipment in which the cord, intended to constitute a carcass reinforcement, is laid down in contiguous arches on a rigid core, via an eyelet fixed on a chain mounted on pulleys in such a way as to surround the core by forming a type of fork. The eyelet performs a to-and-fro movement around the core in such a way as progressively and contiguously to lay down an arch with each outward movement and an arch with each return movement, suitable pressers being used to apply the ends of said arches as they are formed on the rigid core pre-coated with uncured rubber.
The object of the present invention is to provide equipment variants for depositing a reinforcing cord on a core in substantially the same manner.
The invention proposes an apparatus for manufacturing a tire reinforcement, said apparatus being intended for manufacturing a reinforcement constituted from a cord supplied continuously and on demand by a suitable distributor, said apparatus being intended for use in cooperation with a substantially toroidal form on which said reinforcement is built up progressively by laying down arches of said cord, according to a desired trajectory for said cord, on the surface of said form, said apparatus comprising:
a guide member in which the cord may slide freely,
means of displacing said guide member in a cyclical, to-and-fro, movement, to bring said guide member in successive cycles into the vicinity of each of the desired ends for the cord in said trajectory,
pressers close to each end of said trajectory, for applying the cord onto the form at said ends, characterized in that:
the displacement means comprises at least one base arm, said base arm comprising a center of rotation and a conveying head, and control means for imparting to said base arm an oscillatory movement about said center of rotation, the apparatus being arranged so that the conveying head of said base arm directly or indirectly conveys the guide member from one end to the other of said trajectory,
the geometric axis of said center of rotation is, in the working position, entirely exterior to the form.
Reference can be made to the above-cited patent, since the present invention includes not only the process described therein but also to a considerable extent the pressers used to allow formation of a loop and to apply said loop against the core. By way of a reminder, the pressers essentially each comprise a fork and a hammer. Apart from a few details, the presser embodiment described therein could be used as it is, even through a novel form is proposed below for said pressers.
The main differences provided by the invention lie in the cord depositing members and more precisely the actuation of said guide member in which the cord may slide freely (i.e. the eyelet). In other words, the oscillating arm system or systems described below are designed to be able to replace the chain system described in the above-cited patent.
Before embarking on a detailed description of these novel means of actuating the cord guide member, it would be helpful to remember certain useful points.
First of all, it should be noted that, as in the above-cited patent, the term xe2x80x9ccordxe2x80x9d must be understood in a completely general sense, covering a monofilament, a multifilament, an assembly such as for example a cable or a plied yarn, or a small number of grouped cables or plied yarns, whatever the nature of the material and whether or not the xe2x80x9ccordxe2x80x9d is pre-coated with rubber. In the present specification, the term xe2x80x9carchxe2x80x9d is used to designate a portion of cord extending from a singular point to another in the reinforcement armature. All these arches disposed over the entire periphery of the tire form the reinforcement proper. An arch as defined here may be part of a carcass or of a crown reinforcement or of any other type of reinforcement. These arches may be separated by cutting the cord during laying thereof, or they may all be connected together in the finished reinforcement, for example by loops.
Basically, the invention relates to continuous laying of a reinforcing cord, in a configuration as close as possible to the configuration in the finished product. Since the cord is supplied on demand by a suitable distributor comprising, for example, a cord spool and, if applicable, a device for controlling the tension of the cord withdrawn from the spool, the apparatus for manufacturing a reinforcement from a cord cooperates with a form (rigid core or reinforced membrane) on which the tire is manufactured. It is of little significance whether the reinforcement, to be complete, is fabricated in several successive passes of the depositing members described with or without cutting of the cord between two passes.
When positions or directions are defined by the words xe2x80x9cradially, axially, circumferentiallyxe2x80x9d or when radii are mentioned, the reference point is taken to be the core on which the tire is manufactured, or the tire itself, which comes to the same thing. The geometric axis of reference is the axis of rotation of the form.
Likewise, as has already been pointed out in the above-cited patent, the cord depositing members described here also allow the production of a reinforcement, for example a carcass reinforcement, in which the laying pitch of the cord is variable. xe2x80x9cLaying pitchxe2x80x9d is understood to mean the distance resulting from the sum of the space between two adjacent cords and the diameter of the cord. It is well known that, for a carcass reinforcement, the space between cords varies according to the radius at which it is measured. This is not the variation referred to here, which is a variable pitch at a given radius. For this, it is sufficient to vary the speed of rotation of the form as a function of any suitable law without changing the working speed of the guide member. A tire is thus obtained, the carcass reinforcing cords of which, for example for a radial carcass, are disposed at a pitch exhibiting controlled variation for a given radial position.
Various embodiments of the invention may be envisaged. Three main embodiments will be described below. The first embodiment uses a series of three functional oscillating arms. In addition, possible variants are described for this first embodiment. A series of three functional oscillating arms is preferably used for depositing carcass arches extending from one bead to the other of the tire. The second embodiment uses a series of two functional oscillating arms. Furthermore, a variant embodiment is given for this second embodiment. A series of two functional oscillating arms is used, for example, for depositing carcass arches extending from a bead to a shoulder of the tire. The third embodiment uses a single functional oscillating arm, which is sufficient for the simplest laying down to be performed.
When xe2x80x9cnxe2x80x9d functional oscillating arms are used which are arranged in series (n greater than 1), the term xe2x80x9cnth armxe2x80x9d is used to designate the functional oscillating arm to which the cord guide member is directly fixed, the base arm always being the xe2x80x9cfirst oscillating armxe2x80x9d. The oscillating arms are arranged in series in such a way that, in general, the conveying head of the oscillating arm xe2x80x9cpxe2x80x9d (p being less than n) conveys the center of rotation of the oscillating arm xe2x80x9cp+1xe2x80x9d. This is why it is stated above that the conveying head conveys the cord guide member directly, or only xe2x80x9cindirectlyxe2x80x9d (that is to say through the intermediary of one or more other functional oscillating arms). In all the examples described, the geometric axis of the center of rotation of the first oscillating arm is, in the working position, entirely exterior to the form, with which it never comes into contact, that is to say not even via its extensions.
The apparatus causes the cord guide member to describe a movement which is substantially included in a planexe2x80x94the plane of movementxe2x80x94perpendicular to the geometric axis of rotation of the base arm. In another aspect of the apparatus according to the invention, the base arm, or according to the variants, each of the oscillating arms used, is of planar, long-limbed appearance, and the base arm oscillates in this plane of movement, or all the oscillating arms move in parallel, neighboring planes, one of them being very close to this plane of movement, or even merged with this plane of movement, depending on the type of guide member used.
It should also be pointed out that, in another aspect, and without taking account of the respective position of the series of oscillating arms with respect to the form, the invention proposes an apparatus for manufacturing a tire reinforcement comprising a series of arms articulated with one another, the articulations being perpendicular to the plane of movement. Said apparatus, intended for manufacturing a reinforcement constituted from a cord supplied continuously and on demand by a suitable distributor and intended for use in cooperation with a substantially toroidal form on which said reinforcement is built up progressively by depositing arches of said cord according to a desired trajectory for said cord on the surface of said form, comprises:
a guide member in which the cord may slide freely,
means for displacing said guide member in a cyclical, to-and-fro, movement, to bring said guide member in successive cycles into the vicinity of each of the desired ends for the cord in said trajectory,
pressers close to each end of said trajectory, for applying the cord onto the form at said ends,
characterized in that the displacement means comprise at least two arms, i.e. an oscillating base arm and at least one other oscillating arm, said at least two arms each comprising a center of rotation and a conveying head, said at least two arms each oscillating about a geometric axis of rotation, said geometric axis of rotation being parallel to each other, and control means for imparting to said arms oscillatory movements about the respective geometric axes of rotation thereof, the apparatus being arranged so that the conveying head of said base arm conveys the center of rotation of a second oscillating arm and so that the conveying head of the second oscillating arm directly or indirectly conveys the guide member from one end to the other of said trajectory.
The description which follows affords a full understanding of all the aspects of the invention.